sandro

Hey guys whats up,

I'll keep it short...

Last Saturday I disconnected the neg terminal of my battery, Drained the coolant through the drain plug at the bottom of the radiator, then removed and replaced the faulty thermostat with a OEM replacement. Then refilled the reservoir tank with new coolant and reconnected the battery.

The entire job went perfectly without a mess or any problems.

Thennn, about three days later the Check Engine Electronics Warning came back.

I had driven the car approx. 7 times with a faulty thermostat, a total of 100 miles with an average engine temp of 100 Celsius while the Check Engine Electronics light was on before making the repair.

Today I stopped by my guy here in La Jolla to have the codes ran. We ran diagnostics using the OBD2 port under the dash, and tapped directly into the CPU terminal under the hood in the fuse box. We got nothing. The scan tool (a $5000 Master Auto unit, which we've used many times before) was telling us that there were no codes to display.

Has anyone had this happen yet? Whats your thoughts?

Thanks

ohlord

lit up?
Just read via the obd2 port under the dash.
Even if the lamp is off you should show a pending code.
Make sure you properly connected the sending unit by the tstat and that you did not dislodge any vac lines doing the work. Those old M104's in 96 can get pretty brittle vac hoses.

sandro

My thought process was similar to yours. I take meticulous care of all my vehicles for this reason exactly. A sloppy repair can often cause other problems. I'd hate to feel as though my mechanic was not using his equipment properly but I was standing right there with him. He was trying to tell me that the OBD2 scanner would not access the engine codes as usual, and that it would not display any fault codes at all.

My thought was this; I may have replaced the faulty thermostat correctly, but while the battery was disconnected during the repair, the fault code remained in the CPU.

When I began to drive the vehicle again, the stored code reappeared as though the issue was never fixed.

My question to you is whether this is how the sensors and Mercedes CPU works??? Does the car store codes and need a scan tool to remove the code after each repair to "refresh" the system?

ohlord

the worded message
check engine electronics
or the yellow cel lamp?

sandro

both

sandro

Since nobody's jumping in to save the day yet. I'm feeling more and more like my mechanic is an idiot.

I disconnected the battery again yesterday to see if that'll do the trick. If not I'll try checking for codes again.

Does anyone have the Iphone App "REV" ($50 through Itunes). Its a full diagnostics tool complete with gauges, and stores engine dynamics information, AND and OBD2 scanner, and can clear codes???

desired_speeds

I'd look for a shop that has access to SDS and go from there. I'm pretty sure SDS can read much more from the car.